CODEWITHSUNDEEP
dockerdockerfile
zilcuanu
zilcuanu

Reputation: 3715

Does the COPY command create an intermediate container?

Does the COPY command create an intermediate container to copy the files just like RUN command? I did not find any reference to this in the docs.

Upvotes: 0

Views: 211

Answers (1)

David Maze
David Maze

Reputation: 159171

It does not actually create a container.

In the classic builder, Builder.performCopy() goes through the steps of assembling an augmented image: get the base image, create a new layer, actually copy files into the new layer, and then construct a new image. While there is a variable named runConfigWithCommentCmd this just sets the per-layer description that's visible in docker history.

Contrast this with dispatchRun() which actually goes through the mechanics of creating and launching a container. Remember that a container fundamentally wraps a single command, and in the case of COPY there's not an obvious command that could be run (nor, for that matter, is there guaranteed to be any runnable command in the container at all; consider a FROM scratch image).

Upvotes: 2

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